Structure and Method for MOSFET Device

ABSTRACT

The present disclosure provides a semiconductor structure comprising one or more fins formed on a substrate and extending along a first direction; one or more gates formed on the one or more fins and extending along a second direction substantially perpendicular to the first direction, the one or more gates including an first isolation gate and at least one functional gate; source/drain features formed on two sides of each of the one or more gates; an interlayer dielectric (ILD) layer formed on the source/drain features and forming a coplanar top surface with the first isolation gate. A first height of the first isolation gate is greater than a second height of each of the at least one functional gate.

This application is a divisional of U.S. application Ser. No.14/334,842, filed on Jul. 18, 2014, entitled “Structure and Method forMOSFET Device,” the entirety of which is hereby incorporated herein byreference.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs.

Such scaling down has also increased the complexity of processing andmanufacturing ICs and, for these advances to be realized, similardevelopments in IC processing and manufacturing are needed. For example,a three dimensional transistor, has been introduced to replace a planartransistor. Although existing semiconductor devices and methods offabricating semiconductor devices have been generally adequate for theirintended purposes, they have not been entirely satisfactory in allrespects. For example, to introduce three dimensional nanostructure to agate channel raises challenges in a semiconductor device processdevelopment. It is desired to have improvements in this area.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A, 3A, 4A, and 5A are top views of a design layout of the FinFETdevice constructed at various fabrication stages according to someembodiments of the present disclosure.

FIGS. 1B, 5B, and 6B are cross sectional views of the FinFET devicealong the line A-A in FIGS. 1A, 5A, and 6A respectively according tosome embodiments of the present disclosure.

FIGS. 1C, 2A, 3B, 4B, and 5C are enlarged top views of the highlightedstructure of the FinFET device in FIGS. 1A, 3A, 4A, and 5A according tosome embodiments of the present disclosure.

FIGS. 1D, 2B, 3C, 4C, and 5D are cross sectional views of thehighlighted structure of the FinFET device along the line A-A in FIGS.1C, 2A, 3B, 4B, and 5C according to some embodiments of the presentdisclosure.

FIGS. 1E, 2C, 3D, 4D, and 5E are cross sectional views of thehighlighted structure of the FinFET device along the line B-B in FIGS.1C, 2A, 3B, 4B, and 5C according to some embodiments of the presentdisclosure.

FIG. 6A is a top view of a design layout of the FinFET deviceconstructed according to some embodiments of the present disclosure.

FIG. 6B is a cross sectional view of the FinFET device along the lineA-A in FIG. 6A according to some embodiments of the present disclosure.

FIG. 7 is a flow chart of an example method for fabricating the FinFETdevice according to various aspects of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

The present disclosure is directed to, but not otherwise limited to ametal-oxide-semiconductor field-effect transistor (MOSFET), for examplea fin-like field-effect transistor (FinFET) device. The FinFET device,for example, may be a complementary metal-oxide-semiconductor (CMOS)device including a P-type metal-oxide-semiconductor (PMOS) FinFET deviceand an N-type metal-oxide-semiconductor (NMOS) FinFET device. Thefollowing disclosure will continue with a FinFET example to illustratevarious embodiments of the present invention. It is understood, however,that the application should not be limited to a particular type ofdevice, except as specifically claimed.

FIG. 1A is a top view of a design layout 100 of the FinFET deviceconstructed according to some embodiments of the present disclosure. Asshown in FIG. 1A, the design layout 100 includes a PMOS region 102 andan NMOS region 104. The PMOS region 102 is formed in an n-well region,and the NMOS region 104 is formed in a p-well region. The PMOS region102 may be configured on a first active region 106, and the NMOS region104 may be configured on a second active region 108. As shown in FIG.1A, the first active region 106 may include one or more active finlines, e.g., fin lines 106-1, 106-2, and 106-3. Similarly, the secondactive region 108 may also include one or more active fin lines, e.g.,fin lines 108-1, 108-2, and 108-3. The one or more fin lines areconfigured to extend along a first direction 192.

Referring to FIG. 1A, one or more gates 110-115 are configured to extendalong a second direction 194 and formed on the first active region 106and the second active region 108. The one or more gates 110-115 may beconfigured to be parallel to each other. The second direction 194 may besubstantially perpendicular to the first direction 192. In someembodiments, the one or more gates may be configured with the activeregions to form one or more corresponding pull-up (PU) device, pull-down(PD) devices, and pass-gate (PG) devices in a cell. As shown in FIG. 1A,the doped regions, e.g., sources and drains, of each gate may beelectrically and physically connected to the doped regions of theadjacent gate. For example, the sources of the gate 111 may beelectrically and physically connected to the sources of the gate 112 bysharing a common source region defined in the active regions andpositioned between the gate 111 and the gate 112.

Still referring to FIG. 1A, various contacts 120-127 may be formed onthe doped regions for electrically connecting the doped regions. Forexample, a contact 120 may be used to electrically connecting the dopeddrain region of the gate 110 to the doped drain region of the gate 111in the first active region 106. A contact 121 may be used toelectrically connecting the doped drain region of the gate 110 to thedoped drain region of the gate 111 in the second active region 108. Acontact 123 may be used to electrically connecting the doped drainregion of the gate 112 to the doped drain region of the gate 113 in thefirst active region 106. A contact 124 may be used to electricallyconnecting the doped drain region of the gate 112 to the doped drainregion of the gate 113 in the second active region 106. A contact 126may be used to electrically connecting the doped drain region of thegate 114 to the doped drain region of the gate 115 in the first activeregion 104. A contact 127 may be used to electrically connecting thedoped drain region of the gate 114 to the doped drain region of the gate115 in the second active region 106.

One or more long contacts may be configured to extend along the seconddirection 194 and to extend over the first active region 106 and thesecond active region 108. The long contacts have a first dimensionextending along the first direction 192 and a second dimension extendingalong the second direction 194, and the first dimension is substantiallyshorter than the second dimension. The one or more long contacts may beused to electrically connect the doped regions of two adjacent gates onboth the first active region 106 and the second active region 108. Forexample, a long contact 122 may be used to electrically connect dopedsource regions of the gate 111 and the gate 112 extending over the firstactive region 106 and the second active region 108. A long contact 125may be used to electrically connect doped source regions of the gate 113and the gate 114 extending over the first active region 106 and thesecond active region 108.

One or more gate contacts 128-130 may also be formed on thecorresponding gates for routing the gates to the metal routing lines(not shown) correspondingly. The metal routing lines may be formed inone or more metal layers (not shown) on the gates.

Still referring to FIG. 1A, the design layout 100 may include more thanone circuit, e.g., a first circuit 131 and a second circuit 132. In someembodiments, an isolation feature, such as a dummy gate 113 may beformed between the first circuit 131 and the second circuit 132.

FIG. 1B is a cross sectional view of the FinFET device 200 along theline A-A in FIG. 1A according to some embodiments of the presentdisclosure. As shown in FIG. 1B, the FinFET device 200 includes asubstrate 202. The substrate 202 may include bulk silicon (Si).Alternatively, an elementary semiconductor, such as silicon (Si) orgermanium (Ge) in a crystalline structure, may also be included in thesubstrate 202. The substrate 202 may also include a compoundsemiconductor, such as silicon germanium (SiGe), silicon carbide (SiC),gallium arsenic (GaAs), gallium phosphide (GaP), indium phosphide (InP),indium arsenide (InAs), and/or indium antimonide (InSb), or combinationsthereof. Possible substrate 202 may also include asemiconductor-on-insulator substrate, such as Si-on-insulator (SOI),SiGe-on-insulator (SGOI), Ge-on-insulator (GOI) substrates. For example,the SOI substrates may be fabricated using separation by implantation ofoxygen (SIMOX), wafer bonding, and/or other suitable methods.

Referring to FIG. 1B, various doped regions 204 may also be included inthe substrate 202 depending on design requirements. The doped regionsmay be doped with p-type dopants, such as boron (B) or boron fluoride(BF3). The doped regions may also be doped with n-type dopants, such asphosphorus (P) or arsenic (As). The doped regions may also be doped withcombinations of p-type and n-type dopants. The doped regions may beformed directly on the substrate 202, in a p-well structure, in a n-wellstructure, in a dual-well structure, or using a raised structure.

Still referring to FIG. 1B, the FinFET device 200 may include one ormore isolation regions 206. The one or more isolation regions 206 areformed over the substrate 202 to isolate active regions. For example,each isolation region 206 separates the adjacent doped regions 204 inthe substrate 202 from each other. The one or more isolation regions 206may be formed using traditional isolation technology, such as shallowtrench isolation (STI), to define and electrically isolate the one ormore active fins lines. In some examples, the isolation regions 206 mayinclude silicon oxide, silicon nitride, silicon oxynitride, an air gap,other suitable materials, or combinations thereof. The isolation regions206 may be formed by any suitable process. In some examples, theformation of an STI includes a photolithography process, etching atrench in the substrate 202 (for example, by using a dry etching and/orwet etching), and filling the trench (for example, by using a chemicalvapor deposition process) with one or more dielectric materials to formthe isolation regions 206. The filled trench may have a multi-layerstructure such as a thermal oxide liner layer filled with siliconnitride or silicon oxide. A chemical mechanical polishing (CMP) processmay then be performed to remove excessive dielectric materials andplanarize the top surface of the isolation regions 206.

Referring to FIG. 1B, one or more gates 110-115 may be formed on thefirst active region 106, the second active region 108, and the dopedregions 204. The one or more gates 110-115 may include functional gatesand/or dummy polygates. For example, gate 113 may be a dummy polygateconfigured to isolate the circuit 131 and the circuit 132. The dummypolygate 113 may include polysilicon. Gates 110-112, and 114-115 may befunctional gates. The one or more gates 110-115 may be formed by aprocedure including depositing, lithography patterning, and/or etchingprocesses. The deposition processes may include chemical vapordeposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), other suitable methods, and/or combinations thereof.

Still referring to FIG. 1B, sidewall spacers 216 may be formed alongeach of the gates 110-115. The sidewall spacers 216 may include adielectric material such as silicon oxide, silicon nitride, siliconcarbide, silicon oxynitride, or combinations thereof. The sidewallspacers 216 may also include multiple layers. Typical formation methodsfor the sidewall spacers 216 include depositing a dielectric materialover each of the gates 110-115. The dielectric material may be thenanisotropically etched back. The etching back process may include amultiple-step etching to gain etch selectivity, flexibility and desiredover-etch control. In some examples, one or more material layers (notshown), e.g., an interfacial layer, may also be formed between the gateand the corresponding sidewall spacers. The one or more material layersmay include an interfacial layer and/or a high-k dielectric layer.

Still referring to FIG. 1B, one or more source/drain features 208 may beformed on the substrate 202. In some embodiments, the formationprocesses of the one or more source/drain features 208 may includerecessing to form source/drain trenches, and depositing to form the oneor more source/drain features 208 in the source/drain trenches. In someexamples, the one or more source/drain features 208 may be formed byepitaxially growing a semiconductor material layer in the source/drainrecessing trenches. The one or more source/drain features 208 may bein-situ doped during the epitaxial process. For example, the epitaxiallygrown SiGe source/drain features may be doped with boron; and theepitaxially grown Si epitaxial source/drain features may be doped withcarbon to form silicon:carbon (Si:C) source/drain features, phosphorousto form silicon:phosphor (Si:P) source/drain features, or both carbonand phosphorous to form silicon carbon phosphor (SiCP) source/drainfeatures. In some embodiments, an implantation process (i.e., a junctionimplant process) may be performed to dope the source/drain features. Oneor more annealing processes may be performed to activate source/drainepitaxial feature. The annealing processes may comprise rapid thermalannealing (RTA) and/or laser annealing processes. In some embodiments, asource/drain feature is a source region, and the other source/drainfeature is a drain region. The adjacent source/drain features 208 areseparated by a gate, such as a corresponding gate of the gates 110-115as shown in FIGS. 1A-1B. As shown in FIG. 1B, one or more contacts120-126 are formed on the one or more source/drain features 208.

For further clarification, FIG. 1C shows an enlarged top view of thehighlighted structure 300 of the FinFET device in FIGS. 1A-1B accordingto some embodiments of the present disclosure. As shown in FIG. 1C, agate dummy polygate 113 is formed on the active fin line 106-3. FIG. 1Dis a cross sectional view of the structure 300 along the line A-A inFIG. 1C according to some embodiments of the present disclosure. FIG. 1Eis a cross sectional view of the structure 300 along the line B-B inFIG. 1C according to some embodiments of the present disclosure.

According to some embodiments of the present disclosure, an interlayerdielectric (ILD) layer 218 may be formed on the source/drain features208 as shown in FIGS. 2A-2C. The ILD layer 218 may include siliconoxide, silicon oxynitride, or other suitable dielectric materials. TheILD layer 218 may include a single layer or multiple layers. The ILDlayer 218 may be formed by a suitable technique, such as CVD, ALD, andspin-on dielectric, such as spin-on glass (SOG). After forming the ILDlayer 218, a chemical mechanical polishing (CMP) process may beperformed to remove excessive ILD layer 218 and planarized the topsurface of the ILD layer 218.

Referring to FIGS. 3A-3D, a dummy polygate 113 for isolating the firstcircuit 131 and the second circuit 132 is removed to form a trench 220.The dummy polygate 113 may be removed using any appropriate lithographyand etching processes. The etching processes may include selective wetetch or selective dry etch, such that the dummy polygate 113 has anadequate etch selectivity with respect to the doped region 204. Afterremoving the dummy polygate 113, one or more active fin lines in thefirst active region 106 and the second active region 108 are revealed.In some embodiments, the lithography process may include forming aphotoresist layer (resist), exposing the resist to a pattern, performinga post-exposure bake process, and developing the resist to form amasking element including the resist. As shown in FIG. 3A, the maskingelement may be used to expose a region 302 including the dummy polygate113 by any appropriate dry etching and/or wet etching method.

Referring to FIGS. 4A-4D, the ILD layer 218 may be used as mask elementsto further recess the trench 220 within the region 302 to form a trench222. In some embodiments, the remained spacer sidewalls 216 may also beused as mask elements to recess the trench 220. This may be regarded asa self-aligned etching process. In some embodiments, the trench formedusing the self-aligned process is a V-shaped trench 222 as shown in FIG.4C. A portion of the active fin line 106-3 exposed in the trench 220 isremoved as shown in FIGS. 4A-4B. As shown in FIG. 4C, a depth (d1)between a top surface of the source/drain features 208 and a bottom ofthe recessed V-shaped trench 222 may be in a range from about 50 nm toabout 200 nm. In the present embodiment, a mask element with an exposedarea substantially larger than the area of the dummy polygate may beused to etch the substrate to form the trench. For example, the area ofthe exposed region 302 of FIGS. 1A, 3A, and/or 4A is substantiallygreater than the area of the dummy polygate 113 and/or the trench 220.This may provide a lithography friendly process.

Referring to FIGS. 5A-5D, one or more material layers 224 may bedeposited in the trench 222 to form an isolation gate 224. The isolationgate 224 may include a V-shaped bottom conformed to the V-shaped trench222 as shown in FIGS. 5B and 5D. As shown in FIG. 5B, a depth (d2)between a top surface of the source/drain features 208 and a bottom ofthe isolation gate 224 may be in a range from about 50 nm to about 200nm. In some embodiments as shown in FIGS. 5B and 5D, the one or morematerial layers deposited in the trench 222 may include a dielectriclayer 212 and a material layer 224. In some embodiments, the dielectriclayer 212 may include an interfacial layer (IL) and/or a high-k (HK)dielectric layer formed in the trench 222 and conformed to the surfacesof the trench 222. The IL layer may be deposited by any appropriatemethod, such as ALD, CVD, and/or PVD. The IL layer may include siliconoxide (SiO2), or silicon oxynitride (SiON). The HK dielectric layer maybe deposited over the IL layer by any suitable techniques, such as ALD,CVD, metal-organic CVD, PVD, or a combination thereof. The HK dielectriclayer may include one or more material selected from the groupconsisting of HfO2, Ta2O5, and Al2O3, and/or other suitable materials.

Still referring to FIGS. 5A-5E, the material layer 224 may include oneor more metal gate (MG) layers, such as work function metal layer, lowresistance metal layer, liner layer, wetting layer, and/or adhesionlayer. In some embodiments, the work function metal layer may includeone or more materials selected from the group consisting of Tin, TaN,TiAl, TaAl, Ti-included materials, Ta-included materials, Al-includedmaterials, W-included materials, TiSi, NiSi, and PtSi. In someembodiments, the low resistance metal layer may include one or morematerials selected from the group consisting of poly Si with silicide,Al-included materials, Cu-included materials, W-included materials,Ti-included materials, Ta-included materials, TiN, TaN, TiW, and TiAl.The MG layer may be formed by ALD, PVD, CVD, or other suitable process.A CMP process may be performed to remove excessive MG layer and providea substantially planar top surface for the ILD layer 218 and thematerial layer 224. The device work function determined by the workfunction metal layer may be in a range from about 4 eV to about 5 eV.The dielectric layer 212 is formed to provide sufficient insulatingproperty to the material layer 224 filled in the trench 222. Afterforming the dielectric layer 212 and the material layer 224 in thetrench 222, the circuit 131 and the circuit 132 may be sufficientlyelectrically isolated from each other.

In some embodiments, the materials, formation, and layout of thedielectric layer 212 and/or the material layer 224 may also be designedsuch that, a controlled bias voltage may be applied to the isolationgate 224 for effective isolation between the circuit 131 and the circuit132.

In some embodiments, the trench 222 may also be filled by a dielectriclayer. The dielectric layer may be formed using similar method(s) and/orsimilar material(s) as those for the dielectric layer 212 as discussedpreviously. For example, the dielectric layer may include one or morematerials selected from the group consisting of LaO, AlO, ZrO, TiO,Ta₂O₅, Y₂O₃, SrTiO₃ (STO), HfO₂, BaTiO₃ (BTO), BaZrO, HfZrO, HfLaO,HfSiO, LaSiO, AlSiO, HfTaO, HfTiO, (Ba,Sr)TiO₃ (BST), Al₂O₃, Si₃N₄, andsilicon oxynitride (SiON). The dielectric layer used to fill the trench222 may include any suitable materials, such as silicon oxide, siliconnitride, silicon carbide, and/or silicon oxynitride. In some examples,the dielectric layer may be deposited to fully fill the trench 222 toprovide sufficient electrical isolation property. In some embodimentswhen the isolation gate 224 includes a dielectric material filled in thetrench 222, the dielectric material used to fill in the trench 222 isdifferent from the materials used to form the sidewall spacers 216formed along the isolation gate 224. In some examples, the dielectriclayer may partially fill the trench 222. For example a lower portion ofthe trench 222 may be filled by the dielectric layer, and an upperportion of the trench 222 may be filled by the dielectric layer 212 andthe material layer 224. The dielectric layer filled in the lower portionof the trench 222 may have similar function(s) as that of the isolationregion (STI) to separate the circuit 131 and the circuit 132. Thedielectric layer may be formed by ALD, PVD, CVD, or other suitableprocess.

Referring to FIG. 5A, after forming the isolation gate 224, the FinFETdevice 200 includes an isolation gate 224 configured to separate thecircuit 131 and the circuit 132. The gates 110, 111, 112, 114, and 115are functional gates including functional metal gates. In someembodiments, the functional gates may include materials different fromthe materials in the isolate gate. As shown in FIGS. 5B and 5D, a height(h1) of the isolation gate 224 is substantially greater than a height(h2) of each of the sidewall spacers 216 formed along the isolation gate224. The height (h1) of the isolation gate 224 is also substantiallygreater than the height (hf) of the functional gates. In addition, theisolation gate 224 extends into the doped regions 204 and has a bottomlower than that of the functional gates 110, 111, 112, 14, and 115. Thematerial of the isolation gate 224 can be same material as functionalgates, or have different material. Example materials include a purelydielectric material such as SiO2, SiON, Si3N4, high-K dielectric, or acombination thereof in the isolation gate 224. In this example, theprocess flow will be:

-   -   1. isolation gate poly removing and trench etch,    -   2. dielectric deposition (re-fill the isolation gate), and    -   3. functional gate formation (which may further include removing        the poly gate, high-K gate dielectric, work-function metal, and        the low resistance metal formation.)

FIG. 6A is a top view of a design layout 400 of the FinFET deviceconstructed according to some embodiments of the present disclosure.FIG. 6B is a cross sectional view of the FinFET device 650 along theline A-A in FIG. 6A according to some embodiments of the presentdisclosure. In some embodiments, the one or more gates located at theedges of the active fin lines, e.g., gate 110 and/or gate 115 of FIG.1A, may also be removed and the corresponding one or more trenches maybe formed using the ILD layer and/or spacer sidewalls on the sides ofthe gates as mask elements. Dielectric materials, or dielectricmaterials and metal materials may be used to fill the one or moretrenches to form the isolation gates, such as gate 226 and/or gate 228located at the edge of the active fin lines. The formation processesand/or materials of the isolation gates 226 and/or 228 may besubstantially similar to the formation processes and/or materials of theisolation gate 224 as discussed previously. As shown in FIG. 6A, theformation process of the isolation gate 226 at the edge of the activefin lines may include using a mask having an area of the exposed region304 substantially greater than the area of the gate 110. Similarly, theformation process of the isolation gate 228 at the edge of the activefin lines may also include using a mask having an area of the exposedregion 306 substantially greater than the area of the gate 115.

Referring to FIGS. 6A-6B, the FinFET device 650 includes an isolationgate 224 configured to separate the circuit 131 and the circuit 132, andisolation gates 226 and 228 configured to be at the edges of the activefin lines. The gates 111, 112, and 114 are functional gates includingfunctional metal gates. In some embodiments as shown in FIG. 6B, aheight (h1) of the isolation gate 224 is substantially greater than aheight (h2) of each of the sidewall spacers 216 formed along theisolation gate 224. The sidewall spacers 216 and the isolation gates 226and 228 located at the edges of the active fin lines may have asymmetricstructures as shown in FIG. 6B. For example, sidewall spacer 216 aformed on outside of the isolation gate 226 or 228, and an outsideportion of the isolation gate 226 or 228 may have a height (h3),sidewall spacer 216 b formed on inside of the isolation gate 226 or 228,and an inside portion of the isolation gate 226 or 228 may have a height(h4), and the height h3 is substantially greater than the height h4. Inaddition, the isolation gate 226 or 228 may have a bottom lower than thebottom of the functional gates 111, 114, and higher than the bottom ofthe isolation gate 224.

FIG. 7 is a flow chart of an example method 500 for fabricating theFinFET device according to various aspects of the present disclosure.Method 500 includes a process 502 for providing a MOSFET deviceprecursor, a process 504 for depositing an ILD layer over thesource/drain features, a process 506 for removing the dummy polygatebetween the adjacent circuits to form a trench, a process 508 forrecessing the trench using the ILD layer as mask elements, and a process510 for depositing one or more material layers to form an isolationgate. It should be understood that additional processes may be providedbefore, during, and after the method 500 of FIG. 7, and that some otherprocesses may be briefly described herein.

At process 502, the MOSFET device precursor, e.g., the FinFET deviceprecursor 200 is provided. In some embodiments, the MOSFET deviceprecursor includes a substrate, and one or more fins formed in a firstactive region and a second active region over the substrate. The one ormore fins may be separated by one or more isolation regions. One or moregates may be formed over the one or more fins and extending over thefirst active region and the second active region. The one or more gatesmay be formed to extend along a direction that is substantiallyperpendicular to a direction along which the one or more fins may beformed to extend. Source/drain features may be formed in source/drainregions of the MOSFET device precursor.

At process 504, an ILD layer is deposited over the surfaces of each ofthe fins. The ILD layer may include silicon oxide, silicon oxynitride,or other suitable dielectric materials. The ILD layer may include asingle layer or multiple layers. The ILD layer may be formed by asuitable technique, such as CVD, ALD, and spin-on dielectric, such asSOG. A CMP process may be performed to provide a planar top surface ofthe ILD layer.

At process 506, a dummy polygate may be removed to form a trenchdisposed between two adjacent circuits. The dummy polygate may beremoved using any appropriate lithography and etching processes. Theetching processes may include selective wet etch or selective dry etch.After removing the dummy polygate, one or more active fin lines in theactive regions are revealed. In some embodiments, the lithographyprocess may include forming a photoresist layer (resist), exposing theresist to a pattern, performing a post-exposure bake process, anddeveloping the resist to form a masking element including the resist. Asshown in FIG. 3A, a masking element may be used to expose a region 302including the dummy polygate 113 by any appropriate dry etching and/orwet etching method. The mask element may have an area substantiallygreater than the area of the dummy polygate.

At process 508, the trench may be further recessed using the ILD layeras etching mask elements. The remained spacer sidewalls may also be usedas mask elements to recess the trench. For example as shown in FIGS.4A-4B, a portion of the active fin line 106-3 exposed in the trench 220is removed. In the present embodiment, the mask element with an exposedarea substantially greater than the area of the dummy polygate may beused to etch the substrate to form the trench.

At process 510, one or more material layers may be deposited in therecessed trench to form an isolation gate between the two adjacentcircuits. In some embodiments, the isolation gate may include a multiplelayered structure of IL/HK/MG. In some embodiments, the isolation gatemay include a dielectric material fully filled in the recessed trench.In some embodiments, the isolation gate may include a dielectricmaterial filling a lower portion of the recessed trench, and an IL/HK/MGstructure filling an upper portion of the recessed trench. The isolationgate may be formed to electrically isolate the two adjacent circuits.The one or more material layers may be formed using ALD, PVD, CVD, orother suitable process.

It is understood, however, that the present disclosure should not belimited to a particular type of device, except as specifically claimed.For example, the present disclosure is also applicable to other MOSFETdevice. It is also understood that additional steps can be providedbefore, during, and after the method, and some of the steps describedcan be replaced or eliminated for other embodiments of the method.

The present embodiments describe structures and methods for formingMOSFET devices using a self-aligned etching process to form an isolationgate for sufficient electrical isolation between adjacent transistors.The mechanisms involve using the remained ILD layer and the spacersidewalls as etching mask elements to form a trench in the MOSFETdevice. One or more materials layers may then be deposited to fill thetrench to provide sufficient electrical isolation between adjacentcircuits. The mechanisms provide a lithography friendly patterningprocess with improved overlay control without using advanced lithographytools. Thus, no extra cost or area penalty is needed in the presentembodiments. The mechanisms may also provide a fully balancesource/drain epitaxial growth environment, which may improve devicestability, chip speed, cell matching performance, and reduce standbyspecification. The various embodiments of the present disclosure mayachieve an improved uniformity control on source/drain regions, and afully uniform fin-end allocation for both reliability and process marginimprovement.

The present disclosure provides a semiconductor structure comprising oneor more fins formed on a substrate and extending along a firstdirection; one or more gates formed on the one or more fins andextending along a second direction substantially perpendicular to thefirst direction, the one or more gates including an first isolation gateand at least one functional gate; source/drain features formed on twosides of each of the one or more gates; an interlayer dielectric (ILD)layer formed on the source/drain features and forming a coplanar topsurface with the first isolation gate. A first height of the firstisolation gate is greater than a second height of each of the at leastone functional gate.

The present disclosure provides a fin-like field-effect transistor(FinFET) device comprising a substrate including a first active regionand a second active region spaced apart from each other in a firstdirection; a first group of fins configured in the first active region,and a second group of fins configured in the second active region, eachof the first group of fins and the second group of fins extending alonga second direction substantially perpendicular to the first direction;one or more gates configured to extend over the first active region andthe second active region along the first direction, the one or moregates including a first isolation gate and at least one functional gate;sidewall spacers formed on sides of the one or more gates; source/drainfeatures formed on sides of the sidewall spacers; an interlayerdielectric (ILD) layer formed on the source/drain features and forming acoplanar top surface with the one or more gates. A first height of thefirst isolation gate is substantially greater than a second height ofsidewall spacers formed on sides of the first isolation gate.

The present disclosure provides a method of forming a semiconductordevice comprises providing a device precursor including a substrateincluding a first active region and a second active region spaced apartfrom each other in a first direction; a first group of fins configuredin the first active region, and a second group of fins configured in thesecond active region, each of the first group of fins and the secondgroup of fins extending along a second direction substantiallyperpendicular to the first direction; and one or more gates including apolygate configured to extend over the first active region and thesecond active region, each of the one or more gates extending along thefirst direction. The polygate is configured to separate a first circuitand a second circuit. The method further comprises depositing aninterlayer dielectric (ILD) layer over the substrate; removing thepolygate to form a trench; recessing the trench to the substrate usingthe ILD layer as etching mask elements; and depositing one or morematerial layers in the recessed trench to form an isolation gate betweenthe first circuit and the second circuit.

The present disclosure provides a method of forming a semiconductordevice comprising forming a first group of fins in an n-well region anda second group of fins in a p-well region on a substrate; forming one ormore isolation features to separate adjacent fins of the first group offins and the second group of fins; forming one or more gates including apolygate on the first group of fins and the second group of fins, thepolygate configured to separate a first circuit and a second circuit;forming sidewall spacers along the polygate; forming source/drainfeatures on the substrate and on two sides of the polygate; depositingan interlayer dielectric (ILD) layer on the source/drain features;removing the polygate to form a trench between the first circuit and thesecond circuit; recessing the trench using the ILD layer as etching maskelements to a depth lower than bottoms of the source/drain features toform a V-shaped trench; and depositing one or more material layers inthe V-shaped trench to form an isolation gate between the first circuitand the second circuit.

In some embodiments, the recessing the trench further comprises: usingthe ILD layers and the sidewall spacers along the polygate as etchingmask elements.

In some embodiments, the depositing the one or more material layersincludes depositing interfacial layer (IL)/high-k (HK) dielectriclayer/metal gate (MG) in the V-shaped trench.

In some embodiments, the depositing the one or more material layersincludes depositing a dielectric layer in the V-shaped trench.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method of forming a semiconductor device, themethod comprising: providing a device precursor, the device precursorincluding: a substrate including a first active region and a secondactive region spaced apart from each other in a first direction; a firstgroup of fins configured in the first active region, and a second groupof fins configured in the second active region, each of the first groupof fins and the second group of fins extending along a second directionsubstantially perpendicular to the first direction; and one or moregates including a polygate configured to extend over the first activeregion and the second active region, each of the one or more gatesextending along the first direction; wherein the polygate is configuredto separate a first circuit and a second circuit; depositing aninterlayer dielectric (ILD) layer over the substrate; removing thepolygate to form a trench; recessing the trench to the substrate usingthe ILD layer as etching mask elements; and depositing one or morematerial layers in the recessed trench to form an isolation gate betweenthe first circuit and the second circuit.
 2. The method of claim 1,further comprising: forming source/drain features separated by the oneor more gates on the substrate, wherein the ILD layer is formed on thesource/drain features.
 3. The method of claim 1, further comprising:forming spacer sidewalls along each of the one or more gates, whereinthe recessing the trench including using the ILD layer and the sidewallspacers as etching mask elements to form a V-shaped trench.
 4. Themethod of claim 1, wherein the depositing the one or more materiallayers includes depositing interfacial layer (IL)/high-k (HK) dielectriclayer/metal gate (MG) in the recessed trench.
 5. The method of claim 1,wherein the depositing the one or more material layers includesdepositing a dielectric layer in the recessed trench.
 6. The method ofclaim 1, wherein the depositing the one or more material layers includesdepositing a dielectric layer in a lower portion of the recessed trench,and interfacial layer (IL)/high-k (HK) dielectric layer/metal gate (MG)in an upper portion of the recessed trench.
 7. The method of claim 1,further comprising: doping the first active region with n-type dopantsto form an n-well region in a p-type MOSFET (PMOSFET); and doping thesecond active region with p-type dopants to form p-well region inan-type MOSFET (NMOSFET).
 8. A method of forming a semiconductor device,the method comprising: forming one or more fins along a first directionon a substrate; and forming a plurality of gates, including a firstisolation gate and a functional gate, along a second directionsubstantially perpendicular to the first direction, wherein the formingof the plurality of gates includes: forming a first sidewall spaceralong the first isolation gate; forming source/drain features on twosides of each of the plurality of gates; forming a dielectric layer anda metal gate layer in the first isolation gate; and forming the firstisolation gate in a trench in the substrate, such that the dielectriclayer is conformed to a side surface of the first sidewall spacer andextends along the first sidewall spacer and into the substrate such thatthe dielectric layer physically contacts the first sidewall spacer, oneof the source/drain features, and the substrate at a bottom of thetrench, the metal gate layer extending into the substrate to a firstdepth and the one of the source/drain features extending into thesubstrate to a second depth, the first depth being greater than thesecond depth.
 9. The method of claim 8, wherein the dielectric layerincludes a high k (HK) dielectric layer.
 10. The method of claim 8,wherein the dielectric layer includes one or more dielectric materialsselected from the group consisting of SiO2, LaO, AlO, ZrO, TiO, Ta₂O₅,Y₂O₃, SrTiO₃ (STO), HfO₂, BaTiO₃ (BTO), BaZrO, HfZrO, HfLaO, HfSiO,LaSiO, AlSiO, HfTaO, HfTiO, (Ba,Sr)TiO₃ (BST), Al₂O₃, Si₃N₄, and siliconoxynitride (SiON).
 11. The method of claim 8, further comprising:forming one or more isolation regions on the substrate, wherein the oneor more fins are separated by the one or more isolation regions.
 12. Themethod of claim 8, further comprising: forming a first group of fins ina first doped region; and forming a second group of fins in a seconddoped region.
 13. The method of claim 8, wherein the first sidewallspacer includes a first material different from the dielectric layer ofthe first isolation gate.
 14. The method of claim 8, further comprising:forming a second isolation gate at an edge of the one or more fins;forming a second sidewall spacer on an outside edge of the secondisolation gate; and forming a third sidewall spacer on an inside edge ofthe second isolation gate, wherein a height of the second sidewallspacer is greater than a height of the third sidewall spacer.
 15. Amethod of forming a fin-like field-effect transistor (FinFET) device,the method comprising: forming a first active region and a second activeregion on a substrate, such that the first active region and the secondactive region are spaced apart from each other in a first direction;forming a first group of fins in the first active region and a secondgroup of fins in the second active region, such that each fin of thefirst and second groups of fins extends along a second directionsubstantially perpendicular to the first direction; forming one or moregates over the first active region and the second active region alongthe first direction, the one or more gates including a first isolationgate and a functional gate; forming a first sidewall spacer along thefirst isolation gate; and forming a source/drain feature on a side ofthe first sidewall spacer and extending into the substrate to a firstdepth.
 16. The method of claim 15, wherein the first isolation gateincludes a dielectric layer and a metal gate layer, the first isolationgate formed in a trench in the substrate, the dielectric layer conformedto a side surface of the first sidewall spacer and extending along thefirst sidewall spacer and into the substrate such that the dielectriclayer physically contacts the first sidewall spacer, the source/drainfeature, and the substrate at a bottom of the trench, the metal gatelayer extending into the substrate to a second depth that is greaterthan the first depth.
 17. The method of claim 15, wherein a first heightof the first isolation gate is greater than a second height of the firstsidewall spacer of the first isolation gate.
 18. The method of claim 17,wherein the first height of the first isolation gate is greater than athird height of each of the functional gate.
 19. The method of claim 15,further comprising: forming a second isolation gate at an edge of theone or more fins; forming a second sidewall spacer on an outside edge ofthe second isolation gate; and forming a third sidewall spacer on aninside edge of the second isolation gate, wherein an outside portion ofthe second isolation gate and the second sidewall spacer have a fourthheight, wherein an inside portion of the second isolation gate and thethird sidewall spacer have a fifth height, and wherein the fourth heightis greater than the fifth height.
 20. The method of claim 15, furthercomprising forming a second sidewall spacer along the function gate,wherein the source/drain feature extends from the first sidewall spacerto the second sidewall spacer.